In essence the education-focussed Blockly Chromium app for writing offline Picaxe code graphically (and I specifically mention Chromium, not Chrome that comes with a stack of Google-added spy stuff, as does Android unless you take the effort to get rid of it all) works with Android, although I've not tried it as I prefer writing code as text. Programming is a problem, as although you can make a PL2303 or FTDI USB to serial adapter work with Android OK, there doesn't appear to be an option available for programming a Picaxe. The majority of Android devices have an OTG micro USB connector and it's not 100% straightforward to connect this to standard USB and make it work 100%, plus it's not that easy to load USB to serial drivers to Android, I've found. However, I have another Chromium app that talks to a USB controlled radio data link and that works fine in Android as well as Linux (probably works under Windows, too, but I've not tried it), so it looks feasible to get a programming editor working under Android, especially as the Android kernel is based on Linux..
What would be nice is a direct equivalent to the Windows Programme Editor that works reliably under Linux. Axepad is hopelessly flaky, and crashes near-continuously, especially when trying to save a file when it always crashes on all three of the Linux machines I have. I use it because I have to, but the only way to reliably save a file is to cut and paste the text into a text editor and save it. I've lost count of the number of times I've lost code since I switched from using Windows to Linux.
I'm working on trying to get the windows programming editor to work properly under WINE. The alternative is to just write code in a text editor (foregoing all the nice features in the programming editor) and then load the file into Axepad solely to programme the Picaxe, not a great way to work but it does allow files to be saved reliably.